Conventional antilock braking systems (ABS) and electronic stability control (ESC) use a combination of electronic and hydraulic components to function. ABS generally uses three or four wheel speed sensors, for example, to sense when one or more wheels have exceeded the limits of traction between the tire and the road (or other) surface during heavy braking and then reduces braking pressure to wheels that are, or are in danger of, “locking up.” Similarly, ESC uses wheel speed sensors, accelerometers, and other sensors to determine when the vehicle has, or imminently will, lose traction (e.g., oversteer or understeer) due to braking and/or steering inputs and selectively applies braking in an attempt to regain control of the vehicle.
In both cases, the systems use electro-hydraulic actuators to control wheel speed. The ABS electro-hydraulic actuator, for example, tends to “hammer” the pressure rapidly back and forth between the commanded pressure (i.e., a maximum brake line pressure) and a lower pressure designed to reduce or eliminate the wheel slip at a particular wheel. ESC also uses an electrohydraulic actuator and a hydraulic accumulator to increase the brake pressure at one or more wheels to slow those wheels down to create a torque around the vehicle's vertical axis, for example, to counter excessive yaw.
Conventional ABS and ESC systems use multiple complex systems with hydraulic and mechanical means to provide the desired functions. These conventional ABS and ESC systems tend to be overly complicated, heavy, and expensive.